JPS6028026A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which has a good still picture characteristic and decreases head wear by incorporating graphite and fatty acid ester into a magnetic layer. CONSTITUTION:A magnetic recording medium formed with a magnetic layer contg. graphite, more particularly flake graphite having 0.01-3mu average primary particle size at 0.1-10pts.wt. in 100pts.wt. magnetic material and fatty acid ester consisting of C2-22 fatty acid and C2-27 alcohol at 0.05-10pts.wt. in 100pts. wt. magnetic material on a non-magnetic base is manufactured. A suitable amt. of a polishing agent such as Cr2O3, Al2O3, SiC or the like having 6-9 Mohs hardness and carbon black, etc. as an antistatic agent are further added to the magnetic layer. The magnetic recording medium having a long still life, good video S/N and less drop-out is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium with good still image characteristics and less head wear.

Many of the magnetic recording and reproducing decks that have become extremely popular in recent years have a so-called still mode for still images, and therefore magnetic recording media are required to have a long life (still life) that can withstand a long period of still mode. In order to improve the stay life, US patent 3
Various abrasives have been attempted to be developed, as seen in the tl"7ko! issue.On the other hand, when a multi-violet abrasive was added to satisfy the stale life, the head wear became extremely sharp. As a result, the lifespan of the head is shortened.It has been extremely difficult to satisfy both characteristics at the same time.

The first object of the present invention is to provide a magnetic recording medium with a good still life. λth is to provide a magnetic recording medium with less head wear.

As a result of intensive studies to achieve the above object, the present inventors discovered that a significantly effective patch can be obtained by incorporating graphite and fatty acid ester into the magnetic layer, leading to the present invention.

That is, the present invention relates to a magnetic recording medium comprising a magnetic layer provided on a nonmagnetic support, wherein the magnetic layer contains graphite and a fatty acid ester.

The graphite used in the present invention has shapes such as scales, particles, and blocks, and can be used in both natural and artificial forms, but scale-like graphite is particularly effective in reducing head wear. Although the particle size can be selected depending on the purpose, it is preferable to have an average particle size of 0.0/~3μ, which is preferable in terms of electromagnetic conversion characteristics, and if it is too small, the desired effect cannot be obtained.

The amount of graphite added is 0.67 to 70 parts by weight, preferably 0 to 70 parts by weight, based on the weight of the magnetic material.
-1 part by weight. If the amount added is too small, tail life will deteriorate and dropout will occur. If the amount is too large, the electromagnetic conversion characteristics will deteriorate.

The fatty acid ester used in the present invention has 2 to λ carbon atoms.
A fatty acid having a carbon number of λ to λ7 and an alcohol having a carbon number of λ to λ7, preferably a fatty acid having a carbon number of a-it and an alcohol having a carbon number of λ to /4j. Both saturated and unsaturated fatty acids are used. The alcohol mentioned above is preferably a heptahydric alcohol, but a cohydric or trihydric alcohol can also be used.

The male blade af of the fatty acid ester is o, or-io parts, preferably o, i-1 parts, based on 10θ weight parts of the magnetic material. The above fatty acid esters may be used alone or in combination of two or more.

As a result of further studies, the present inventors found that in addition to the combination P4tJ, Cr2O3, alumina, garnet, α
- It has been found that the effect of improving the stale life can be particularly increased by using an abrasive having a Mohs hardness of more than or equal to 0, preferably 0 to 0, such as Fe20B or SiC.

The amount of abrasive added is θ, 7 to 700 parts by weight of the magnetic material.
It is 30-joiit division, preferably 1-joiit division.

'f The center line average roughness Ra of the support is 0.031μ (c
ut offO, or wm), preferably no
.

By setting it to 0λjμ or less, electromagnetic conversion characteristics can be improved.

When the support is too smooth, causing poor running performance in a VTR, or when the support is scraped and attached to the magnetic layer, resulting in signal dropouts/Use of supports with different smoothness on both sides. , λ, application of back coat layer, 3. Countermeasures can be taken by applying I4 detergent to the diamagnetic side of the support. Among these, the most effective is ycg, which clearly separates the functions of each layer.

It is. It is preferable to add powder such as carbon black or graphite to the back coat layer to prevent static electricity.

It is preferable to further add carbon black to the magnetic layer. Carbon black has an antistatic effect and is effective in preventing signal dropouts due to dust adhesion.

The carbon black used has an average particle size of 3
It is 0 mμ or less, preferably io to 3o tnμ, and more preferably lj to cormμ.

The amount of carbon black added is 0.00 parts by weight per 100 parts by weight of the magnetic material. /-10 parts by weight, preferably 0.1 to 5 parts by weight.

It will be easily understood by those skilled in the art that the IFK present invention will be explained in more detail with reference to Examples below.

Therefore, the invention should not be limited to the examples below.

In addition, all "parts" in the examples indicate parts by weight.

Example I CO-containing r Fe2O3 100 parts Graphite [scaly, average -J part particle size 0.3μ] Fatty acid ester (butylstear 1 part rate carboxyl group-containing salt vinyl acetate, 20 parts combined polyurethane resin - 0 part polyisocyanate 20 parts Abrasive (Cr20B) 6 parts Methyl ethyl ketone ljO parts Butyl acetate ljO parts The above composition was dispersed in a ball mill, the viscosity was adjusted to Hiroo voids, and then a polyester support (RaO, θ) of is μ thickness was dispersed.
3jμ) on top to a thickness of jμ (same thickness for the following examples)! A sample (A/) was prepared.

Comparative Example 1 *A comparative sample (A) was prepared by removing graphite and fatty acid ester from the composition of Example 1.

Example 2 CO-containing r-Fe203 100 parts Graphite (scaly, average -5 part particle size 0.3μ) Fatty acid ester (butylstear 1 part rate) Carboxyl group-containing salt vinyl acetate Kyodo 2a part combined polyurethane resin 20 parts Poly Isocyanate 20 parts Abrasive (Cr20a) 4 parts Carbon black (average-order particle size JOmμ) Methyl ethyl lactone 110 parts Butyl acetate Izo parts A practical sample (A3) was prepared in the same manner as in the practical inversion.

In addition, practical samples were prepared in which the particle sizes of graphite were changed to 0.2μ, lμ, and 3μ, respectively, with the above composition, and the sizes were Aμ, Jl;, and jX16.4 in that order.

Comparative Example 2 From the composition of Example 2, a comparative sample C7) in which both graphite and fatty acid ester were removed, a comparative sample (Aff) in which only graphite was removed, and a comparative sample (A?) in which only fatty acid ester was removed were prepared. did.

Example 3 A magnetic layer with the composition of Example 2 was placed on the - side of a polyester support (Ra: 0.03zμ), and a back coat layer with the following composition was placed on the other side, and the same thickness was applied in cases where the thickness was jμ or less C) A practical sample (flat 1O) was prepared.

Carbon black (average particle size
mμ) Nitrocellulose 30 parts Polyurethane resin 3 parts Vinylidene chloride/acrylonide /j part Lithium copolymer polyisocyanate 23 parts Calcium carbonate jO part α=Fe203 2 parts Methyl ethyl ketone toooo Butyl acetate zooo Comparative example 3 Fatty acid in the composition of Example 2 A comparison sample (J@A//% 1/J) was prepared for the ester.

In addition, a comparative sample (A/
≠) was prepared.

Example 4 ((i1 layer composition)) Co-containing FaOx (x:/, II) 100 parts graphite (scaly, average -7 parts primary particle O1 reference μ) Fatty acid ester (amylstear 7 parts rate) Fatty acid ester (ethylstear 1 part fatty acid (C myristic acid) 0, 1 part silicone oil (dimethylbo) 1 part carbon black (average particle size io part size 10
Voiceμ Toluene 150 parts Butyl acetate /10t! d5 ((pack layer composition)) Carbon black (average - defective grains 100 parts size 30
mμ) Graphite (scaly, average -ioo partial grain defects 1 ref.μ)
) Carboxyl group-containing salt-vinyl acetate Kyodo 7-part combined polyurethane resin 3-part polyisocyanate jO-part Merck powder! O part Calcium carbonate 50 parts Goethite 50 parts Methyl ethyl ketone 1000 parts Cyclohexanone 300 parts The above magnetic layer composition was subjected to a three-roll mill and a sand grinder, and the above pack layer composition was dispersed and prepared using an attritor. A practical sample (A/j) was prepared by coating the above magnetic layer on a polyester support with Ra=θ and 0.20μ and a pack layer on the other side.

Example 5 In Example 3, the polishing punishment was applied to 100 parts of the magnetic material at 0.3 parts, /, 0 parts, 3 parts, 70 parts, 20 parts, respectively.
30 parts, sample k (I[lCA/
AXA/ 7, A/ I, A/ri, yaλ0, Al1,
A, Z2) were prepared.

Each magnetic tape was evaluated using a VH8 type VTR. The STEIL LIFE HVTR was set in the STALE mode, and the time until the image disappeared was expressed in minutes. 7'C-Head wear was measured by running the tape for ioo hours, and the wear degree of the fcvk head was expressed in μ. The video S/N ratio is expressed as rdBJ relative to the standard tape. Dropout was visually measured on a monitor screen and expressed as "number W of 1/jH or more."

The results are shown in the table. Comparison sample 47.161. By comparing with A, it was found that only when a combination of graphite and fatty acid ester is present in the magnetic layer, both the stale life and head wear characteristics are good, and the video S/N and dropout are also good. Recognize.

In comparative samples A/tXA/-2 and A/J, in which the fatty acid ester of A3 was replaced with another lubricant, the effect of the combination with graphite is not clear.

Comparative samples A/DA, which contained an increased amount of abrasive, had the disadvantage of high head wear.

By comparing the samples A/XAJ and A/0 according to the present invention, it can be seen that addition of cardan black to the magnetic layer and coating of the pack layer are more preferable. Bian 3~
By comparing &4, the particle size of graphite is O0j
It can be seen that μ or less is preferable.

Claims (1)

[Claims] A magnetic recording medium comprising a magnetic layer provided on a non-magnetic support, characterized in that the magnetic layer contains graphite and a fatty acid ester.